The present invention relates generally to an ESR-CIG system. The ESR portion is an electroslag refining apparatus and the CIG portion is a cold wall induction guide tube apparatus, also referred to herein as a cold wall induction guide mechanism and a cold finger nozzle mechanism. More particularly, the invention relates to the design of the copper funnel portion of the CIG. Most particularly, the invention relates to the maintenance of an insulation gap between the individual copper segments that make up the CIG.
Maintenance of the insulation gaps between copper segments is important to the effectiveness of the induction heating system in accomplishing the numerous applications that can be made of the refining apparatus including atomization processing and relate generally to direct processing of metal passing through an electroslag refining operation. One example of molten metal refining is referred to as electroslag refining, and is illustrated and described in U.S. Pat. No. 5,160,532--Benz et al, assigned to the same assignee as the present invention, the disclosure of which is hereby incorporated by reference.
In an electroslag process, a large ingot of a preferred metal may be effectively refined in a molten state to remove important impurities such as oxides and sulfides that may have been present in the ingot. Simply described, electroslag refining comprises positioning a metal ingot over a pool of molten material in a suitable vessel or furnace where the molten material pool may include a surface layer of solid slag, an adjacent underlayer of molten slag and a lowermost body of refined molten ingot metal. The ingot is connected as an electrode in an electrical circuit including the molten metal pool, a source of electrical power and the ingot. The ingot is brought into contact with the molten slag layer and an electrical current is caused to flow across the ingot/molten slag interface.
This arrangement and process provide electrical resistance heating of the slag and melting of the ingot at the noted interface with the molten ingot metal passing through the molten slag layer as a refining medium to become a part of the body of refined ingot metal. It is the combination of controlled resistance melting and passage of the molten ingot metal through the molten slag layer that refines the ingot metal to remove impurities such as oxides, sulfides, and other undesirable inclusions.
However, one component of the ESR/CIG melting system is the copper funnel that forms the walls of the cold-walled-induction guide which comprises several copper segments that result from slotting an otherwise axisymmetric funnel, the slots being added to avoid melting the copper funnel itself as a result of the surrounding induction coils which provide for the penetration of the electric field throughout the funnel and into the liquid metal in the cold-walled-induction guide. The copper funnel has been found to experience a high level of thermal and mechanical strain related to the onrush of liquid metal that occurs when the ESR-CIG system is started. This thermal and mechanical strain has resulted in liquid metal flowing between the several copper segments the cold-induction guide when it has solidified as "fins." These "fins," in addition to causing a short-circuit of the insulation gap, apply extensive force to the vertical walls of the segments resulting in decreased useful life thereof.
Thus, it is important to develop methods and systems for maintaining the insulation gaps between copper segments in order to prevent liquid metal from flowing between the segments and solidifying as fins. Such methods and systems should at least reduce if not eliminate the solidifying of liquid in the gaps, at least reduce if not eliminate the short circuits in the copper funnel and at least reduce if not eliminate the external mechanical forces on the segment walls thereby increasing the segments useful life. Such methods and systems for maintaining the insulation gaps between the copper segments of the orifice could include, among other means, providing a layer of insulating material for establishing a fixed minimum space between each segment; for insulating each segment from the next segment and applying a means over the top of the layer of the insulation material for filling uneven areas in the layer and for sealing the gaps between each segment.